Radiosignaling system



A. N. GOLDSMITH. RADIOSIGNALING SYSTEM. APPLlcmou mw mm2. 19u.

QM; bornes ALFRED N. GOLDSMITH, 0F YORK, N. Y., ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION 0F 'NEW YORK.

RADIOSIGNALIN'G SYSTEM.

Application led March 29. 1917. Serial No.

To all whom it may concern:

Be it known that I ALFRED N. GoLDsMrrH,

a citizen of the United. States, residin at New York, in the county ofNew York, tate of New York, have invented certain new and usefulImprovements in Radiosignaling Systems, of which the following is aspecification. A

My present invention relates to the production of radio frequencycontinuous electrical oscillations for use in a. signaling system, andto ymeans for controlling theamplitilde of such oscillations inaccordancewith the variations fin the amplitude ofia signaling currentsuch, Afor examplepas a current produced by sound waves.

It has been found that an velectron discharge device `of the type knownas pliotron consisting of a filamentaryelectron emitting cathode, ananode and a discharge controlling grid inclosed 4in an envelop evacuatedto such a degree .that ythe device is operatively independent ofpositive gas ionization at voltages above tlus ionization voltagecharacteristic of whatever `residual gas remains Vwithin the envelop,may be utilized to advantage for the reduction of radio fre uencycontinuous oscillations. Devices of t is type have been described byD1'. Irving Langmuir in a paper published in the Prooeed'n s `of theInstitute of Rad-o Engineers of eptember 1915. In order to utilize suchoscillations for radio signaling and particularly for radio telephony,it is necessary to modulate or vary the amplitude of the oscillationssupplied to the radiating s stem in accordance with variations in thesignaling current. A pliotron ma also be used to advantage as anamplifier o variable currents since by reason of its property of beingoperable at high voltages the energy output which maw he obtained from asingle device is much greater than that obtainable from previously knownelectron discharge devices in which gas ionization takes place andaffects the operation even at low voltages. One of the objects of myinvention is to provide an improved system in which pliotrons are usedfor supplying modulated radio frequency currents to a radiating system.

A further object of my invention is to provide a circuit arrangement inwhich a Single source of energy may be utilized for Specification ofLetters Patent.

Patented July 20, 1920.

supplyingv the operating current or potential for a lurality ofpliotrons which are used for di erent purposes.

carrying my invention into effect I utilize an electron dischargedevice, which is preferably a pliotron, for producing radio frequencyoscillations, I impress an oscillating potential obtained from thisoscillator upon the secondary o f a transformer which is connected tothe grid circuits of a lurality of pliotrons connected in para lel inorder to produce an amplified radio frequency current which will supplythe desired amount of energy for the operation of the radiating system.The radio frequency potential which is supplied to the grid circuits ofthe amplifiers is modulated by means of another pliotron whose platecircuit includes the transformer secondary. The resistance of themodulating pliotron is varied by varying the potential of its grid inaccordance with variations in the signaling current. As the resistanceof the modulating pliotron is varied a variable amount of current iscaused to flow therethrough from the transformer secondarv and thepotential across the secondary is varied accordingly. As a result thecurrent output of the ampli- Hers will vary in accordance with thevariations in the signaling current. In order that a single source ofcurrent may be utilized for heating a number of filaments of thedifferent pliotrons I arrange the system in such a way that one terminalof each such lament is at earth potential. This arrangement also enablesme to utilize a single source of energy for supplying the operatingcurrent for the oscillators and for the power am liliers.

he novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims. The inventionitself, however, both as to its organization and method of operation,together with further objects and advantages thereof will best beunderstood by reference to the following description taken in connectionwith the accompanying drawing in which I have indicateddiagranimatically one way in which my invention may be carried intoeffect.

The pliotron 1 comprising the usual filamentary cathode 2. anode 3 andgrid 4 inclosed in an evacuated envelop is employed turns which maysiderable amount radio frequency oscillations, and l term this themaster oscillator. 'l`lie anode and grid of the master oscillatorI areconnected to'a circuit which comprises an inductance 5 and a variablecondenser (i by means ol which the circuitl isA tuned to the frequencyof the oscillations which are to he produced. Energy for the operationofthe lmaster oscillator is supplied to the plate circuit by thedlrectcufrren't gem erator 7 which is connected to the cathode :ind'ariode','rthe cathodeA being grounded atS. `)ondfrnserltl'prevents the directcurrent component of the plate current from flowing through inductance.An indncta'nce 1t) 1n series with the generator ianda condenser- 11 inparallel therewith serve to smooth out any irregularities in the currentsuppl-y and a choke coil 12 which 1 term a radio frequency chokel coilprevents the radio freuexicyy component of the plate current from owingthrough the generator 7. .It has been Vcustomary heretoore to" regardany large inductance as achoke coil for radio frequency currents. 'Allinducta'nces howe'rcr have distributed capacity f between the be44considered as a condenser in 'parallel with the'4 inductance. Thiscapacity will serve to by-pass a con of radio frequency energy forproducing unless' the capacityris such that the` natural period of thecoilv resulting from its 1ni radio frequency the battery 14, a radiocapacity is Y approximately ductance and which is to equal to that ofthe frequency he choked out. If the coil is so designed, it will act asa high impedance to the desired currents and by the term radio frequencychoke coil I mean a coil which is designed ito offer a high impedance ofthis sort to the radio frequency currents which will tend to flow in thecircuit in which it is employed.

'l'he cathode 2 of the -master oscillator is connected to a point 13 inthe inductance 5 which point maybe varied as desired in order toobtain'the most efficient operation of the system. It will usually befound desirable to apply to tential with respect to the filament inorder to adjust the normal current through the pliiotron to a point onits operating chal;- aeteristic which will be most favorable for itsoperation. This potential, which will usually be negative, may beobtained from frequency choke coil 15 being included in the circuitto.prevent radio frequency currents from flowing through the battery 14.The condenser 16 will prevent the short-eircuiting of battery 14 throughinductance 5. rEhe direct current generator 17 with an induetance 18 inseries therewith furnishes current for heating the cathode ofthe masteroscillator and also lier the cathodes of thecther pliotrons asindicated. lV'hile the circuit which l have the grid a definitepodesmihed above For producing oscillations is the one which l preferother circuit arrangements may be used without departing from the scopeof my invention.`

The indnctance 5 forms theI primary of a rad-io freqaiency transformer,one end of the secondary 19 of which is connected to the cathodes of aseries of amplifying pliotrons 20, 2l, 22, which are all connected inmultiple. Wliule l. have indicated only three pliotrons thus connected,as many may he used in this way as desired or as may be ynecessary tosecure the desired output in the radiating system.V A suitably selectedpoint 23 in the secondary 19' is connected to the grids of theamplifiers through a con'- dcuser 24 and a resistance 25. llhe grids of'these ampliliers are maintained ata definite potential with respect tothe cathodes by means Aof the battery 14, a radio frequency choke coil26 in series therewith pre venting radio frequency currents from flowingthrough the battery and the condenser lpreventi'ng the Shortcircuitingof the battery through secondary 19 of theitransformer.Without the resistance 25 thereis a tendency for the amplifiers tooscil'late at an audio frequency or tooseillate at radio frequencybecause of the internal capacity coupling of the pliatrons between theelectrodes. rl`he resistance 25, however, effectively prevents thesetting up of theseundesirable oscillations.

The `generator T furnishes Vcurrent for the operation of the platecircuits of the amplifiers and the anodes of the amplifiers in thepresent case are connected through a condenser 2 and a variable contact28 to in dnetance 29 which is included in circuit with the antenna 30.By connecting the plate circuit of the amplifiers to the antenna in thisway a definite best impedance may be secured as a load on theamplifiers. It has been found that the amplifiers operate mosteliiciently when the impedance of the load circuit has a particularvalue, this value de pending u on the characteristics of the amplifiers.ince the antenna system as a Whole may not. have the desired impedance linclude in the load circuit only enough of the antenna impedance to givethe desired value. It will of course be lapparent that the output of theamplifiers may be supplied to other load circuits than an antenna ifdesired.

The output of the amplifiers is a function of the voltage impressed upontheir grids from the transformer secondary 19, this voltage being due tothe alternating current o f radio4 frequency produced in inductance 5.If the transformer secondary 19 be shunted by a variable resistance thevoltage across it will vary as a Jfunction of the value of theresistance. For a very high resistance the voltage will be practicallythe same as for ail open circuit and the output of the amplifier will bea maximum. l* or a short circuit the input voltage'and high frequencyoutput of 'the amplifier will both be zero. For intermediate values'ofresistance the amplifieroutput will depend uponthe particular value ofthe resistance.

In the present case I einplo a pliotron 31, as `a'} variable resistances unt to the transformer secondary 19, the resistance of the pliotron`between cathode and anode being la function of its gridvoltage` Whenthis voltage is highly negative with respect to thecathode theresistance is very high` as the grid'volta e is made less negative orevendpositiveA t e resistancebecomes correspon ing smaller. AA definiteoperating potential maybe supplied tothe grid of pliotron 31V by meansof the connection 32 to 'batteryl through the radio frequency chokeco1l'33. This pliotron I term the infodulator' `Whilefthe pliotron isthe preferred form of modulator, other forms of L, controllablel,elements may be adapted for lthe dsiredvpurpose.

i' 'In the system illustrated Ethe potential of the ,modulator grid isvaried 7in accordance wfitlrvariation's in a telephone'current producedbyn'vthe.telep'honetransmitter 34 which is included in a local circuitv'with lbattery 35 and the `primarily 36 ofan audio frequencytransformer. he telephone current thus produced 4is amplified byimpressing the potential of the transformer `secondary 37 upon the ii-idof a pliotron amplifier 38. Current for the operation of this am lifieris derived from the battery 14 throng the connection 39'.` rThe platecircuit of amplifier 38 in-A ciu-des the primary 40 of a transformer thesecondary 41 of which is in circuit with the `grid of modulator 31. Thegrid of ampliier 38 is given a definite operating potential by means ofthe battery 42. By this arrangement 'the potential of the grid ofmodulator 31 is made to vary in accordance with variations in thetelephone current. The resistance ofthe modulator and hence the radiofrequency potential applied tothe grids of the amplifiers and theoutputof the amplifor y the modulator fiers are, as a result, allvariedlin accordance with thevariations,in the telephone current. hadiofrequency choke ooit-13 prevents the alternating component .of theamplifier current from flowing through generator 7.

It Will be noted that the modulator is connected across all oftransformer secondary 19` while only a portion of secondary 19 isconnected in the grid circuits of the amplifiers. This arrangement maybe reversed if desired or both connections may be made to the same pointin secondary 19. The object et varying the points of connection is tosecure the most eiiicient operating voltages late circuit and theamplifier gridA circuits. It will usually he found desirable to connectthe circuits in the manner indicated, as by this connection themodulator plate circuit will operate at u higher voltage than thatapplied to the amplifier grids and this condition will be most suitablefor efficient operation. i

While I have described a system for producing radio frequency currentswhich are modulated in accordance with variations in a locally producedtelephone current, my invention is by no means limited in its usefulnessto this particular purpose. It will be apparent that the telephonecurrent employed may equally well be one whiclris derived from a longdistance line throll'gh' one or more line amplifiers such as 38. It willalso be apparent that the system may be utilized for radio telegraphy byvarying the modulator grid potential in accordance with variations ina.telegraphc current` l. have also described the electron dischargedevices used as pliotrons since by reason of the ability of suchdevicesl to operate at high voltages, their use is preferable wheneverit is desired to control more than a few watts of electrical energy. Itwill be apparent, however, that in so far as the principle of operationis concerned other devices in which gas ionization or conduction plays apart in the operation may be equivalents of liotrons.

llihat Iclaim as new and desireto secure by Letters Patent of the UnitedStates is:

V1. The combination in a radio signaling system of a pliotron oscillatorhaving a resonant circuit associated with its anodeand grid and soarranged that radio frequency oscillations will be produced in aninductance included in said resonant circuit, a seccnd inductancecoupled to the first mentioned inductance and connected to the gridcircuits of a pluralit 1 of' pliotron amplifiers connected in parallel,a pliotron modulator having its cathode and anode connected to saidsecond inductance, means for producing a current by sound Waves, apliotron amplilier for amplifying the current thus produced and forvarying the grid potential of said pliotron modulator in accordance withvariations in the amplified current, a com-l mon direct current sourceof potential for supplying energy to the plate circuits of' saidpliotron oscillator and said first mentioned amplifiers, a common directcurrent 'source of potential for fixing the normal potential of thegrids of said oscillator, first mentioned' amplifiers and modulator, andsupplying current to the plate circuit of the second mentionedamplifier, radio frequency choke coils for reventing radio frequencycurrents from owing through said direct current sources and a directconnection between the plate circuits of the amplifiers and a radiatingantenna, said connection being variable in order to adjust the impedancein the load circuit of the, amplifiers to a. collie suitable for themost efficient operar. tion of the system.

2. The combination in a. radio sigmilinrg,1 system of n plioltlron.oscillator having o (munt circuit usslwiuted with its inode :rnd gridand so arranged that radin frequency oscillations will be reduced u i enmdiur tance included in sai resonnnt circuito sccond inductance coupledto the ,first uientioned inductenoe and connected to the. Jrid circuitsof n plurality of liotron, om) 1` ers connected in parallel, a p intronmo ulator having its. cathode end anode. cciilnotedto said secondinductencemeans for vordying the grid potentiel-einem nlietroirinoulator in accordance .with variations 1n e current produced, by soundwaives, e common d1 rect current sourceoif potentiel for supplyingenergy to the plete circuits of Seid pho,- tron oscillator and saidamplifiers, o common direct current source of .potentiel for fixing thenormal potentiel of the grids oft said osoillutor,l amplifiers andmodulator! radio frequency choke coils fory preventing radio frequencycurrents. from -owing through said diirect current sources onda, directconnection between the plete circuits of the amplifiers and a radiatingantenna, said connection being variable in order to adjust the impedancein the load circuit of the am. ilers to a value suitaihle for the mosteicient operation of the s stern. Y

3` The combination in a radio, signaling system of means ier producinAradio frequency oscillations and supplying them to an nduetance in thegrid circuits of a C{nlnrnlity of pliotron amplifiers connecte inparallel, a. pliiotron modulator having its cathode and anode COnnctedto said inductrunce, means for varying the grid otentiol of seidmodulator in accordance willi variations in a signaling current, a.common direct current source of potential for fixing the normalpotential of the grids of seid nmulifiers und modulator, radio frequencyIh Ye coils for preventing radio frequency currents from flowing throughsaiddirect current source, and a direct connection between the platecircuits oi the amplifiers dnd a radiating antenne., seid connectionbeing variable in order to adiustthe impedance in the lood circuit ofthe amplifiers to n value suitable for the most eiicient operation ofthe s stem.

l. he combination in a radio signalling system of n pliotron oscillatorhaving a resonant circuit associated therewith 'and so arranged thatradio frequency ,oscillations will be produced in an inductaince,included in said resonant circuit o second inductence coupled to thefirst mentioned ind'uctence and connected inthe gridcircults of a luraltof pliotron amplifiers connecte in para lel, a pliotron modulatorhav-ing its cathode and anode connected to Said Second iuductonce, meansfor applying to the eethode and :inode of Suid modulator it difierontvoltuge than that applied 4to the grid circuits of the amplifiers, endIneens for varying the grid potentiel o'snid modulator in accordancewith variations in n signaling current.

5. The combination in n radio signaling system of o pliotron oscillatorhaving e resi onent circuit associated therewith and so wronged. thatIndio frequency oscillations. will be produced in an inductence includedin said resoimnt circuit, :i second inductnnce coupled to the firstmentioned induct'anoe :ind connected in the grid circuits of a plu,-rolity of pliotron amplifiers 4connected in parallel, :i pliotronmO-(luhttor l'lwlg its cathode and anode connected to Vseid Secondinductaincc, ineens for varying the grid potentiol of said modulatingpl'otron in acordance with variations in o signal, 0'- cur rent an earthconnection to thecnt "Iddon oi' said oscillator, ompliliersandmodulator-fond n common direct. current source. of .potentiel forsupplying energy to the plete circuits of said oscillator und saidempliier.

6. The combination in nfredio signaling system of plotron oscillatorherring :t resonant circuit associated therewith `end so, arranged thatradio 4frequency oscillations will be produced in en inductanceincliided in said resonant circuit, e second inductence coupled to thefirst mentioned inductaqnce and connected in the grid circuits of a lurnlity of pliotron amplifiers connect in perellel, a. pliotron,modulator having its cathode and anode connectedv to Sndseconrlinductunce, means for varying the grid potcntial of said modulntor, inaccordance with variations in s signaling current, an earth connectiontothe cathodes of seid oscillator, amplifiers and modulator, e commondirect current source of potentiel for supplying energy to the platecircuits of seidv oscillator und said amplilier, and e common directcurrent source of potential Jfor fixing the normal potential of thegrids of said oscillator, am pliers and modulator.

7: The combination in n radio signaling system of n pliotron oscillatorhaving e reS.- orient circuit associated therewith and so arranged thatradio frequency oscillations will he produced 1n an lnductnnce includedin e said resonant circuit,` a second inductance coupled to the iirstmentioned inductonce andconnected in the grid circuits of a, plurnlt ofpliotron amplifiers connected in por lel, a. pli'otron modulator havingits cathode and anode connected to said second inductance, means forvaryin the grid potential of seid modulating p otron in accordance withvariations in a signalin current, an earth connection to the catho es ofsaid oscillator, amplifiers and modulator, a

common direct current source of potential -for supplying energy to theplate circuits of said oscillator and said amplifier, a common directcurrent source of potential for fixing the normal potential of the gridsof said oscillator, amplifiers and modulators, and radio frequency chokecoils for preventing radio frequency currents from fiowing through saiddirect current sources.

8. The combination in a radio signaling system of means for producingradio frequency oscillations and supplying them to an inductance in thegrid circuits of a plurality of pliotron amplifiers connected inparallel, a pliotron modulator having its cathode and anode connected tosaid indnc tance, means for varying the grid potential of said modulatorin accordance with variations in a signaling current, a common directcurrent source of potential for fixing the normal potential of the gridsof said amplifiers and modulator and radio frequency choke coils forpreventing radio frequency currents from flowing through said directcurrent source.

9. The combination in a radio signaling system of means for producingradio frequency oscillations and supplying them to an inductance inthegrid circuits of a plurality of pliotron amplifiers connected inparallel, a pliotron modulator having its cathode and anode connected tosaid inductance, means for varying the grid potential of said modulatorin accordance With Variations in a signaling current and a common directcurrent source of potential for fixing the normal potential of the gridsof said amplifiers and modulator.

10. The combination in a radio si maling system of means for producingra io frequency oscillations and supplying them to an indnctance in thegrid circuits o l' a plurality of pliotron amplifiers connected inparallel, a pliotron modulator having its cathode and anode connected tosaid inductance`r means 'for varying thc grid potential of saidmodulator in accordance with variations in a signaling current, an earthconnection to the cathodes of said amplifiers and modulator and a commondirect current source of current for supplyingr heating current to thecathodes of said amplifiers and modulator.

11. The combination in a radio signaling system of means for producingradio frequency oscillations and supplying them to an indnrtanre in thegrid circuits of a plurality of pliotron amplifiers connected inparallel, a variable resistance device connected to said inductance,means for varying the resistance of said device in accordance withvariations in a signaling current and means for applying to saidvariable resistance device a different voltage than that applied to thegrid circuits of. the amplifier.

12. The combination in a radio signaling system of an antenna and aplurality of pliotron amplifiers arranged to supply modulated radiofrequency currents to said antenna, the plate circuits of saidamplifiers being connected to said antenna by direct connections, andsaid connections being variable in order to adjust the impedance in theload circuit of the amplifiers to a value snitable for the mostefficient operation of the supply system.

In Witness whereof, I have hereunto set my hand this 27th day of March,1917.

ALFRED N. GOLDSMITH.

